Hydraulic Fitting Sizes Chart

Because connectors and ports have so many uses in hydraulic hose piping systems, you must accurately identify them before using or replacing them on a tube or hose.

Manufacturers classify the major thread characteristics: pitch, angle, diameter, and shape, using I.D.s like ASME B1.1 and ISO 261.

The International Organization for Standardization, SAE International, the British Association, the Deutsches Institut für Normung, the American Society of Manufacturing Engineers, and the American National Standards Institute are some organizations working on them.

Hydraulic Fitting Sizes

You can find hydraulic hose use everywhere, from automotive engineers building machines to construction vehicles and more.

Finding the right fittings can be challenging as there are so many SAE thread sizes and metric sizes to scour through.

In our guide, we have the most common hydraulic hose options. By the end, you’ll know more about the thread angle, the flanges used, JIC fitting sizes, and O-ring seal options.

With a hydraulic fitting size chart for each option, you shouldn’t spend too long to get the right hose fitting for your task. (Read Bad Boy Mower Hydraulic Problems)

How Do I Know What Size Hydraulic Fittings I Need?

To get the proper hydraulic hose, you’ll need a few things. A fluid port and connector identification tools are used most often.

  • Calipers: Perfect for measuring inner and outer diameters of fittings and threads
  • Thread Pitch Gauge: Made to measure the number of threads per inch and thread to thread spacing used for metric applications.

Thread Measurement

Check the threads of your fluid pipe or tube before measuring them. Damaged threads can cause inaccurate measurements. After checking your threads, measure their diameter and note it. An I.D./O.D. caliper is acceptable. Compare the dimensions in this guide to your measurements.

Calculate thread spacing in threads per inch after measuring thread diameter. Measuring thread-to-thread lengths in metric connections To acquire an accurate value, ensure the thread pitch gauge fits correctly. Note the values and compare them to the figures in this guide.

Measurement of Four-bolt Flanges

Use a caliper to measure the porthole diameter of your bolt. Note this and measure the distance from center to center of your bolt holes, then take note of the most extended spacing.

Dash Numbers

Tube and fluid pipe diameters are designated by dash numbers, widely used to identify and order fittings. Just the numerator is used when identifying a fluid pipe or tube with a dash number.

The denominator (usually 16) is ignored. Size -8 corresponds to 8/16″ or 1/2″.

Unlike imperial measurements, metric measurements give the actual size of a tube or pipe. For example, for M12 x 1.0, the threads are 12 mm in diameter with a 1.0 mm thread spacing.

Flare Fittings

Flare fittings are compression fitting that is generally used with aluminum, copper, or mild steel tubing, although other metals are also utilized. A flare fitting is used to fasten the tapered end of flared tubing to the fitting during assembly.

This creates a tight seal that can withstand tremendous pressure. In addition, flare adapters are extremely reliable, making them suited for most mission-critical applications and inaccessible areas.

NPT Dryseal Tapers

The American National Standard Pipe Thread (ANSPT) is a technical standard adopted in the United States for the specific screw threads used for pipes and threaded pipes. These standards include straight thread and tapered series for applications needing pressure-tight sealing, stiffness, or both. Threaded pipes effectively seal hydraulic fluid, steam, gases, and liquids.

The taper added to NPT threads helps them produce a tight seal by compressing the sides of the threads rather than the straight thread connections or compression connections. On the other hand, parallel or straight connections create no seal and only hold the two pieces together. Depending on the application, you can use pipe threads with or without thread sealants.

ORFS Fittings (O-Ring Seal Face)

An O-Ring Face Seal fitting makes an O-ring right on the fitting’s face to eliminate leaks in high-pressure hydraulic systems. ORFS connections use O-rings inserted in the face groove of the fitting, providing a leak-proof flared tube fitting that should eliminate hydraulic leaks.

To produce a metal-to-metal seal, the O-ring compresses against the flat face sleeve, creating a leak barrier. O-ring face seal connections can stop hydraulic system leaks up to 6,000 psi. ORFS connectors are also popular because they are readily built or dismantled in the field to replace O-rings or even the entire assembly.

JIC Fittings

Joint Industry Council (JIC) flare fittings have a 37° sitting surface. JIC connections are widely used in fuel distribution and fluid power, especially where exceptionally high-pressure resistance (10,000 psi) is required.

JIC connections are extensively used in diagnostic and test point settings in the fluid power industry. For example, you can use a three-way JIC connection to take pressure readings and perform system and circuit diagnostics.

British Standard Pipe (BSP)

Except for the USA, which favors the NPT standard, practically all countries use BSP screw threads. In addition to externally threaded pipes, BSP technical standards cover inside threaded pipes.

In all nations that have adopted the BSP, the pipefitting and plumbing industries acknowledge it as a standard. A BSP thread can be either taper or parallel and paired with either longscrew or jointing thread types.

Japanese Units of Measurement

Professionals on the Japanese islands used to rely on the Chinese-based traditional Japanese units of measure. Since 700, the Chinese measurement system has been widely adopted in Japan. Imperial Japan eventually adopted the metric system, and all traditional units were defined in meters and kilograms.

Taiwanese and Korean measurement units are developed from these ancient units. Japan had three rival measurement systems during the twentieth century: English, Metric, and Traditional Japanese. The metric system was eventually established, and it is currently used in all commerce, though conventional measurements are still used in some niche applications.

Split-Flange Fittings

Split-flange connectors are generally utilized in high pressure, vibration, and shock tolerance applications. In addition, split-flange connections can assist secure hose-to-pipe or rigid-line connections.

Flange fittings are also simply constructed and very resistant to loosening. Because split-flange connections come in at least 700 different configurations and sizes, it’s easy to choose one that fits your application.

What Size Is A Number 12 Hydraulic Fitting?

Here you can find the most common connection sizes and the associated hydraulic fitting chart that goes with them.

American Connections

National Pipe Tapered Fuel (NPTF)

When the male and female threads mate, a seal is formed (i.e., threads deformation). It’s called a dry seal thread. You can use Teflon and pipe dope for extra sealing. (Read AC Compressor Oil Capacity Chart)

The NFPA does not recommend the connection for hydraulic applications, however it is prevalent in fluid pipe systems. Although NPTF and BSPT connectors look similar, they are not compatible.

National Pipe Tapered Fuel (NPTF)

Inch sizeDash sizeThreads per InchMale Thread O.D. (in) Female thread O.D (in) 
1⁄8-22713⁄320.413⁄80.38
1⁄4-41817⁄320.541⁄20.49
3⁄8-61811⁄160.685⁄80.63
1⁄2-81427⁄320.8425⁄320.77
3⁄4-12141 1⁄161.0510.98
1-1611 1⁄21 5⁄161.321 1⁄41.24
1 1⁄4-2011 1⁄21 21⁄321.661 19⁄321.58
1 1⁄2-2411 1⁄21 29⁄321.901 13⁄161.82
2-3211 1⁄22 3⁄82.382 5⁄162.30

National Pipe Straight Mechanical (NPSM)

Male and female NSPM connectors have straight threads, with males having a 300 internal chamfer and females an inverted 300 seat.

When male and female mate, a mechanical connection is created. The tapered seat creates a leak-proof connection in fluid power systems.

A chamfered NPTF male and an NPSM female can seal.

National Pipe Straight Mechanical (NPSM)

Inch sizeDash sizeThreads per InchMale Thread O.D. (in) Female thread O.D (in) 
1⁄8-22713⁄320.413⁄80.38
1⁄4-41817⁄320.541⁄20.49
3⁄8-61411⁄160.685⁄80.63
1⁄2-81427⁄320.8425⁄320.77
3⁄4-12141 1⁄161.0510.98
1-1611 1⁄21 5⁄161.321 1⁄41.24
1 1⁄4-2011 1⁄21 21⁄321.661 19⁄321.58
1 1⁄2-2411 1⁄21 29⁄321.901 13⁄161.82
2-3211 1⁄22 3⁄82.382 5⁄162.30

JIC 37° Flare (SAE J514)

This connection’s JIC male and female have a 37º flare seat and straight threads. The male and female flare seats seal when the straight threads are linked. It is mechanically held together by the straight threads of each side

While most SAE J514 threads resemble SAE 45o flare threads, their seating angles differ.

JIC 37° Flare (SAE J514)

Inch sizeDash sizeThread SizeMale Thread O.D. (in) Female thread O.D (in) 
1⁄8-25⁄16 - 245⁄160.319⁄320.27
3⁄16-33⁄8 - 243⁄80.3811⁄320.34
1⁄4-47⁄16 - 207⁄160.4413⁄320.39
5⁄16-51⁄2 - 201⁄20.505⁄320.45
3⁄8-69⁄16 - 189⁄160.5617⁄320.51
1⁄2-83⁄4 - 163⁄40.7511⁄160.69
5⁄8-107⁄8 - 147⁄80.8813⁄160.81
3⁄4-121 1⁄16 - 1211⁄161.0610.98
7⁄8-141 3⁄16 - 121 3⁄161.191 1⁄81.10
1-161 5⁄16-121 5⁄161.311 1⁄41.23
1 1⁄4-201 5⁄8 - 121 5⁄81.631 9⁄161.54
1 1⁄2-241 7⁄8 - 121 7⁄81.881 13⁄161.79
2-322 1⁄2 - 122 1⁄22.502 7⁄162.42

SAE 45° Flare (SAE J512)

SAE 45° Flare (SAE J512)

They are used in low-pressure applications, including refrigerant and fuel lines and automotive plumbing. The connector’s threads engage in producing a tight mechanical connection, with the seal formed on the 45° flare seat.

SAE 45° Flare connections seats are identical to JIC 37° Flare connectors.

SAE 45° Flare (SAE J512)

Inch sizeDash sizeThread SizeMale Thread O.D. (in) Female thread O.D (in) 
1⁄8-25⁄16 - 245⁄160.319⁄320.27
3⁄16-33⁄8 - 243⁄80.3811⁄320.34
1⁄4-47⁄16 - 207⁄160.4413⁄320.39
5⁄16-51⁄2 - 201⁄20.5015⁄320.45
3⁄8-65⁄8 - 185⁄80.639⁄160.57
1⁄2-83⁄4 - 163⁄40.7511⁄160.69
5⁄8-107⁄8 - 147⁄80.8813⁄160.81
3⁄4-121 1⁄16 - 1411⁄161.0610.99
7⁄8-141 1⁄4 - 121 1⁄41.251 5⁄321.16
1-161 3⁄8 - 121 3⁄81.381 9⁄321.29

SAE Straight Thread O-ring (O-Ring Boss)

A sealing face, chamfer, and straight thread define the O-Ring Boss female port. It has an O-ring and a straight thread. Squeezing the O-ring into the chamfer creates the seal.

The male and female threads link together mechanically. This connection is popular in high-pressure hydraulic systems.

SAE Straight Thread O-ring (O-Ring Boss)

Inch sizeDash sizeThread SizeMale Thread O.D. (in) Female thread O.D (in) 
1⁄8-25⁄16 - 245⁄160.319⁄320.27
3⁄16-33⁄8 - 243⁄80.3811⁄320.34
1⁄4-47⁄16 - 207⁄160.4413⁄320.39
5⁄16-51⁄2 - 201⁄20.5015⁄320.45
3⁄8-69⁄16 - 189⁄160.5617⁄320.51
1⁄2-83⁄4 - 163⁄40.7511⁄160.69
5⁄8-107⁄8 - 147⁄80.8813⁄160.69
3⁄4-121 1⁄16 - 121 1⁄161.0610.98
7⁄8-141 3⁄16 - 121 3⁄161.191 1⁄81.10
1-161 5⁄16 - 121 5⁄161.311 1⁄41.23
1 1⁄4-201 5⁄8 - 121 5⁄81.631 9⁄161.54
1 1⁄2-241 7⁄8 - 121 7⁄81.881 13⁄161.79
2-322 1⁄2 - 122 1⁄22.502 7⁄162.42

O-Ring Face Seal (SAE J1453)

This connector has excellent leak resistance and can withstand up to 6000 psi. The male half has an O-ring and a straight thread. The female half has a machined flat surface and a straight thread.

A seal is formed when the male O-ring is pushed into the female flat surface seat. The female half’s swivel nut secures the connection.

O-Ring Face Seal (SAE J1453)

O-Ring Face Seal (SAE J1453)

Inch sizeDash sizeThread SizeMale Thread O.D. (in) Female thread O.D (in) 
1⁄4-49⁄16 - 189⁄16 - 180.5617⁄320.51
3⁄8-611⁄16 - 1611⁄160.695⁄80.63
1⁄2-813⁄16 - 1613⁄160.823⁄40.75
5⁄8-101 - 1411.0015⁄160.93
3⁄4-121 3⁄16 - 1213⁄161.191 1⁄81.11
1-161 7⁄16 - 121 7⁄161.441 3⁄41.36
1 1⁄4-201 11⁄16 - 121 11⁄161.691 5⁄81.61
1 1⁄2-242-1222.001 15⁄161.92

Four-Bolt Flange (SAE J518 and ISO 6162)

The Four-Bolt Flange connects 1/2″ – 3″ hose and tube in fluid power systems. The O-ring on the male half and the smooth face of the female port seal (with the O-ring seating on the ring groove of the male). The connection is kept together by two clamp halves.

These come in two pressure groups:

  • Standard (code 61)
  • High pressure (code 62)

Four-Bolt Flange (SAE J518 and ISO 6162)

Inch sizeDash sizeCode 61 Bolt SpacingCode 61 Flange O.D.Code 62 Bolt SpacingCode 62 Flange O.D.
1⁄2-81 1⁄21 3⁄161 19⁄321 1⁄4
3⁄4-121 7⁄81 1⁄221 5⁄8
1-162 1⁄161 3⁄42 1⁄41 7⁄8
1 1⁄4-202 5⁄1622 5⁄82 1⁄8
1 1⁄2-242 3⁄42 3⁄83 1⁄82 1⁄2
2-323 1⁄162 13⁄323 13⁄163 1⁄8
2 1⁄2-403 1⁄23 5⁄16n/an/a
3-484 3⁄164n/an/a

O-Ring Pilot Threads

This connection is common in commercial and vehicle air conditioning. The O-ring is compressed between the male and female parts, forming a seal.

Threads mesh firmly to establish a mechanical bond.

O-Ring Pilot Threads

Inch sizeDash sizeMale Thread Female thread 
Thread sizeThread O.D.Thread sizeThread I.D.
3⁄8-65⁄8 - 185⁄85⁄8 - 189⁄16
1⁄2-83⁄4 - 183⁄43⁄4 - 1611⁄16
5⁄8-107⁄8 - 187⁄87⁄8 - 1413⁄16
3⁄4-121 1⁄16 - 161 1⁄161 1⁄16 - 1413⁄16
Inch sizeDash sizeLong pilot Short pilot 
Bead O.D. (in)Pilot Length (in)Bead O.D. (in)Pilot Length (in)
3⁄8-60.520.280.520.19
1⁄2-80.520.390.640.19
5⁄8-100.770.390.770.19
3⁄4-120.770.390.910.19

How Are Hydraulic Pipe Fittings Measured?

In every corner of the globe, industrial devices and equipment are created and built. For example, hydraulic systems alone require a vast array of fittings and adapters, each with its own set of sealing mechanisms and thread shapes.

While the sealing method may typically be determined by appearance, thread shapes can be difficult and time-consuming to differentiate when equipment upgrades or repairs are required.

Knowing the correct thread is crucial when choosing replacement components for maintenance and repair.

When the improper part is chosen, the thread can be damaged during installation, compromising the fitting’s pressure holding capability and seal reliability. Identifying threads quickly and correctly can aid in the maintenance of safe, productive, and lucrative operations.

Threads on hydraulic tube fittings come in six different types:

  • UN/UNF
  • NPT/NPTF
  • BSPP (BSP, Parallel)
  • BSPT (BSP, Tapered)
  • Metric Parallel
  • Metric Tapered

How to Identify Thread Type and Size

1. Determine if Thread is Tapered or Parallel

UN/UNF and BSPP are parallel threads, while NPT/NPTF and BSPT are tapered threads.

Metric Tapered and Metric Parallel are self-explanatory.

In some circumstances, you can complete this step by visual inspection. For example, parallel threads have the same diameter from start to finish, whereas tapered threads get smaller as they move closer to the end of the fitting.

If this isn’t clear from looking at the fitting, compare it with the parallel jaws of a caliper. In addition, the presence of an O-ring or the removal of a tube nut is usually indicative of a parallel male thread.

Three of the six possible thread types are eliminated by completing step 1.

2. Determine the Pitch

This can be determined by comparing thread counts using a pitch gauge or measuring and calculating the number of threads within a certain distance.

With a pitch gauge, comparing threads against an illuminated backdrop is much easier. However, because several thread pitches are similar, it’s a good idea to try a few different gages before determining which one is right for you.

Because most threads have a specific pitch, the outcome of Step 2 will further reduce the possible thread forms.

3. Determine the Size

The proper technique for Step 3 will be determined – or helped predict in certain circumstances – by combining the outcomes of steps 1 and 2.

The thread size is determined using one of two ways, depending on whether the thread is a pipe thread (NPT/NPTF, BSPT, BSPP) or not (UN/UNF, Metric Parallel, Metric Tapered).

Remember that just because it’s tapered (as the example in Step 1) doesn’t indicate it’s a pipe thread (e.g., Metric Tapered). Pipe thread can also be parallel (e.g., BSPP).

Determine the size of the pipe thread by comparing it to a nominal size profile (a handy tip: pipe diameters up to 2″ nominal size can be obtained by measuring the actual outside diameter, subtracting 14″, and then rounding off).

You can ascertain the absolute size of a non-pipe thread by using a caliper to measure the outside diameter (major diameter).

4. Designate the Thread

Technically, this last step has nothing to do with locating the thread. Rather, it’s a way of describing the thread type in an industry-standard manner that others can comprehend.

Identify Thread Summary

All that is required to distinguish between the various thread types is this reference chart (see table 1), a caliper, and a thread gage. The thread gage is the most crucial tool (or pitch gage).

This tool, which resembles a sawtooth, determines hose thread pitch. It has a set number of serrations within a set distance and is (typically) labeled as such.

The hose pitch of metric threads is defined as the distance between each thread in millimeters (mm).

Pitch or angle is defined as the number of threads per inch for all other threads.

Type Of Hydraulic Fittings

How Do I Know What Type Of Hydraulic Fittings I Have?

Here is a quick breakdown and example of the international hose connections you can find with their associated size table for the different categories.

British Standard Pipe

There are two types of British connections: British Standard Pipe Parallel (BSPP) and British Standard Pipe Tapered threads (BSPT) (BSPT).

Parallel British Standard Pipe (BSPP)

The male end has a 300 seat, which the female swivel’s tapered nose seals with.

Note: Although the male end is similar to the American National Pipe Straight Mechanical (NPSM) male, the thread pitches are not interchangeable.

British Standard Pipe

Inch sizeDash sizeThread SizeMale Thread O.D. (in) Female thread O.D (in) 
1⁄8-21⁄8 - 283⁄80.3811⁄320.35
1⁄4-41⁄4 - 1933⁄640.5215⁄320.47
3⁄8-63⁄8 - 1921⁄320.6519⁄320.60
1⁄2-81⁄2 - 1413⁄160.823⁄40.75
5⁄8-105⁄8 - 147⁄80.8813⁄160.80
3⁄4-125⁄8 - 141 1⁄321.0431⁄320.97
1-161 - 111 5⁄161.301 7⁄321.22
1 1⁄4-201 1⁄4 - 111 21⁄321.651 9⁄161.56
1 1⁄2-241 1⁄2 - 111 7⁄81.881 25⁄321.79
2-322 - 112 11⁄322.352 1⁄42.26

e Tapered (BSPT)

The seal forms in the threads when a tapered male connects with a tapered female.

Because of their distinct sizes and thread form, the BSPT male end and the National Pipe Tapered Fuel (NPTF), male end are not compatible.

British Standard Pipe Tapered (BSPT)

Inch sizeDash sizeThread SizeMale Thread O.D. (in Female thread O.D (in) 
1⁄8-21⁄8 - 283⁄80.3811⁄321 25⁄32
1⁄4-41⁄4 - 1933⁄640.5215⁄321 25⁄32
3⁄8-63⁄8 - 1921⁄320.6519⁄320.60
1⁄2-81⁄2 - 1413⁄160.8219⁄320.75
5⁄8-105⁄8 - 1413⁄160.8813⁄160.80
3⁄4-123⁄4 - 1413⁄161.0431⁄320.97
3⁄4-161 - 111 5⁄161.301 7⁄321.22
1 1⁄4-201 1⁄4 - 111 21⁄321.651 9⁄161.56
1 1⁄2-241 1⁄2 - 111 7⁄81.881 25⁄321.79
2-322 - 111 7⁄82.351 25⁄322.26

Flat Face Port with British Standard Pipe Parallel Threads (ISO 1179-1)

DIN 3852, Part 2

The parallel thread form creates a seal with various tubes, rings, or washers. The seal forms between the male end and the female end’s smooth flat metal surface as the hose and fitting connect.

Metric Threads (mm) on a Flat Face Port (ISO 9974-1)

Part 1 of DIN 3852

The parallel threads create a seal with a variety of rings or washers. The seal forms between the male end and the female end’s smooth flat surface when the hose and fitting connect together. (Read SAE Socket Sizes)

Metric threads (ISO 261)

Flat Face Port with British Standard Pipe Parallel Threads (ISO 1179-1)

Metric Thread SizeMale Thread O.D. (mm)Female Thread I.D (mm)
M8 x 1.087
M10 x 1.0109
M12 x 1.51210.5
M14 x 1.51412.5
M16 x 1.51614.5
M18 x 1.51816.5
M20 x 1.52018.5
M22 x 1.52220.5
M24 x 1.52422.5
M26 x 1.52624.5

Hydraulic Fitting Sizes Chart

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